Diagnostic test for vitamin b12

ABSTRACT

An isolated nucleotide sequence or fragment thereof encoding the porcine intrinsic factor, wherein the porcine intrinsic factor comprises an amino acid sequence having at least 85% amino acid sequence identity to an amino acid sequence selected from the group consisting of SEQ ID NO: 3, SEQ ID NO: 6, and SEQ ID NO: 9. The invention also encompasses an isolated nucleic acid sequence or fragment thereof comprising, or complementary to, a nucleotide sequence having at least 85% nucleotide sequence identity to a nucleotide sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO: 7. The porcine intrinsic factor can be use is an assay to determine the quantity of vitamin B 12  in a biological sample.

This application is a division of pending U.S. application Ser. No.11/052,128, filed Feb. 7, 2005, herein incorporated in its entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to reagents for diagnostic testing, and moreparticularly, reagents for diagnostic testing carried out by automatedimmunoassay analyzers.

2. Discussion of the Art

Anemia is the major disorder related to low serum vitamin B₁₂ levels.Megaloblastic anemia (MA), characterized by elevated mean corpuscularvolume (MCV), has been found to be due to vitamin B₁₂ deficiency. Therelationship between vitamin B₁₂ levels and MA is not always clear inthat some patients with MA will have normal vitamin B₁₂ levels;conversely, many individuals with vitamin B₁₂ deficiency are notafflicted with MA. Despite these complications, however, in the presenceof MA (e.g., elevated MCV) there is usually serum vitamin B₁₂deficiency. A major cause of vitamin B₁₂ deficiency is perniciousanemia. This disease is characterized by poor vitamin B₁₂ uptake,resulting in below normal serum vitamin B₁₂.

There a number of conditions that manifest themselves as low serumvitamin B₁₂ levels, including iron deficiency, normal near-termpregnancy, vegetarianism, partial gastrectomy/ileal damage, oralcontraception, parasitic competition, pancreatic deficiency, treatedepilepsy, and advancing age. Disorders associated with elevated serumvitamin B₁₂ levels include renal failure, liver disease, andmyeloproliferative diseases.

Intrinsic factor binds vitamin B₁₂. This characteristic enables thedetection of and measurement of the quantity of vitamin B₁₂ inbiological samples. In conventional preparation of intrinsic factor, theintrinsic factor protein is isolated from porcine tissue by means of anexpensive, tedious, and time-consuming process.

cDNA cloning using reverse transcriptase-polymerase chain reactiontechnique (RT-PCR) is well-known in the art. The designing of primersbased on homology known for this particular protein in other species(such as human, mouse and rat) and selecting the appropriate PCRconditions to obtain cDNA require a significant amount of planning andexpertise in the PCR-based cloning technique.

U.S. Pat. No. 3,591,678 discloses a process for purifying intrinsicfactor by a batch chromatography process that utilizes an ion exchangeresin. Impure intrinsic factor is dissolved in a buffer solution havingrelatively low pH and ionic strength, and the resultant solution iscontacted with a cellulosic exchange resin. The resin is separated fromthe solution and the purified intrinsic factor is eluted therefrom witha buffer solution having a higher pH and ionic strength than the buffersolution in which the impure intrinsic factor was dissolved.

U.S. Pat. No. 4,447,528 discloses a radioassay procedure and reagent kittherefore for detecting auto-blocking antibody, such as auto blockingantibody which interferes with the complexation of intrinsic factor withvitamin B₁₂. A receptor, i.e., intrinsic factor, is immobilized on asupport and the amount of ligand, i.e., vitamin B₁₂, capable of bindingtherewith in the presence of a biological fluid sample is determined.

U.S. Pat. Nos. 5,227,311 and 5,459,242 disclose a method for purifyingan aqueous intrinsic factor solution which contains R-protein. Themethod involves adding to the intrinsic factor solution an amount ofcolloidal silica to disperse lipid emulsion, an amount of cobinamidesufficient to bind substantially all of the R-protein in the solutionand an amount of an intrinsic factor affinity resin sufficient to bindthe intrinsic factor in the solution, washing the bound cobinamide andthe R-protein from the resin, eluting the intrinsic factor from theresin, and dialyzing the eluted intrinsic factor. Also disclosed is akit for conducting an assay for cobalamins which includes a conjugate ofmicroparticles and purified intrinsic factor.

U.S. Pat. No. 5,350,674 discloses a non-isotopic competitive assay forvitamin B₁₂, utilizing intrinsic factor labeled with horseradishperoxidase, by coupling via heterobifunctional cross-linking agents. Inaddition, a method for stabilizing the resultant conjugates bypretreatment with N-ethylmaleimide is disclosed.

Prior investigators have disclosed the cDNA sequences encoding humanintrinsic factor (Genbank Accession No. M63154), mouse intrinsic factor(Genbank Accession No. L24191) and rat intrinsic factor (GenbankAccession No. J03577). However, the cDNA sequence of the porcineintrinsic factor is not known. Therefore, prior to this invention,recombinant porcine intrinsic factor protein could not be produced.

Porcine intrinsic factor is typically isolated from the tissue of theduodenum of a hog (e.g., Sus scrofa). This isolation is a tedious,expensive, and time-consuming procedure, and the yields are low. Thenative intrinsic factor isolated by currently used procedures lacksconsistency in its purity and in its resulting performance in animmunoassay. Therefore, it would be desirable to produce porcineintrinsic factor in large quantities and to isolate porcine intrinsicfactor in a single-step affinity isolation process. Recombinant proteinproduced in this manner would have consistent performance in adiagnostic immunoassay.

SUMMARY OF THE INVENTION

The present invention includes an isolated nucleotide sequence orfragment thereof encoding porcine intrinsic factor, wherein the porcineintrinsic factor comprises an amino acid sequence having at least 85%amino acid sequence identity to an amino acid sequence selected from thegroup consisting of SEQ ID NO: 3, SEQ ID NO: 6, and SEQ ID NO: 9.

Additionally, the present invention encompasses an isolated nucleic acidsequence or fragment thereof comprising, or complementary to, anucleotide sequence having at least 85% nucleotide sequence identity toa nucleotide sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO: 4, and SEQ ID NO: 7.

The nucleotide sequences described above encode a functionally activeporcine intrinsic factor that binds vitamin B₁₂. The present inventionalso includes purified proteins and fragments thereof encoded by theabove-referenced nucleotide sequences.

Additionally, the present invention includes a method of producingporcine intrinsic factor comprising the steps of: isolating a nucleotidesequence comprising or complementary to a nucleotide sequence encoding aporcine intrinsic factor an amino acid sequence having at least 85%identity to an amino acid sequence of SEQ ID NO: 3, SEQ ID NO: 6, andSEQ ID NO: 9; constructing a vector comprising: i) the isolatednucleotide sequence operably linked to ii) a promoter; and introducingsaid vector into a host cell for a time and under conditions sufficientfor expression of the porcine intrinsic factor. The host cell may be,for example, a eukaryotic cell or a prokaryotic cell. In particular, theprokaryotic cell may be, for example, E. coli, cyanobacteria or B.subtilis. The eukaryotic cell may be, for example, a mammalian cell, aninsect cell, a plant cell or a fungal cell (e.g., a yeast cell such asSaccharomyces cerevisiae, Saccharomyces carlsbergensis, Candida spp.,Lipomyces starkey, Yarrowia lipolytica, Kluyveromyces spp., Hansenulaspp., Trichoderma spp. or Pichia spp.). Other fungal hosts such asRizopus spp., Aspergillus spp. and Mucor spp. may also be utilized.

Moreover, the present invention also includes a vector comprising: anisolated nucleotide sequence comprising or complementary to a nucleotidesequence encoding the porcine intrinsic factor having an amino acidsequence having at least 85% amino acid identity to an amino acidsequence selected from the group consisting of SEQ ID NO: 3, SEQ ID NO:6, and SEQ ID NO: 9, operably linked to a regulatory sequence (e.g., apromoter). The invention also includes a host cell comprising thisvector. The host cell may be, for example, a eukaryotic cell or aprokaryotic cell. Suitable eukaryotic cells and prokaryotic cells are asdefined above.

Additionally, the present invention includes an isolated nucleic acidsequence or fragment thereof which hybridizes, under moderate or highstringency conditions, to a nucleic acid sequence selected from thegroup consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO: 7.

The present invention also encompasses an isolated nucleic acid orfragment thereof, which hybridizes, under moderate or high stringencyconditions, to an isolated nucleic acid sequence encoding porcineintrinsic factor, wherein the amino acid sequence of the porcineintrinsic factor has at least 85% identity to an amino acid sequenceselected from the group consisting of SEQ ID NO: 3, SEQ ID NO: 6, andSEQ ID NO: 9.

It should be noted that the present invention also encompasses isolatednucleotide sequences (and the corresponding encoded proteins) havingsequences comprising, corresponding to, identical to, or complementaryto at least about 70%, preferably at least about 80%, and morepreferably at least about 85% identity to SEQ ID NO: 1, SEQ ID NO: 4,and SEQ ID NO: 7. (All integers (and portions thereof) between 70% and100% are also considered to be within the scope of the present inventionwith respect to percent identity.) Such sequences may be derived fromany source, either isolated from a natural source, or produced via asemi-synthetic route, or synthesized de novo. In particular, suchsequences may be isolated or derived from sources other than describedin the examples (e.g., bacteria, fungus, algae, C. elegans, mouse orhuman).

Furthermore, the present invention also encompasses fragments andderivatives of the nucleic acid sequences of the present invention(i.e., SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO: 7), as well as of thesequences derived from other sources, and having the above-describedcomplementarity, identity or correspondence. Functional equivalents ofthe above full length sequences and fragments are also encompassed bythe present invention.

The method of this invention involves cloning the cDNA encoding porcineintrinsic factor by RT-PCR (Reverse Transcriptase-Polymerase ChainReaction). The design of the primers was based on the homology thatexists between the intrinsic factor cDNA sequences of human, mouse, andrat.

Intrinsic factor isolated by methods currently used in the art providesan inconsistent result with respect to purity, and, consequently,performance in an assay. By employing the method and protein of thisinvention, recombinant intrinsic factor having consistent properties canbe produced. The method of this invention reduces cost and simplifiesisolation. Furthermore, the results of the assays using porcineintrinsic factor show improved consistency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the expression of recombinant porcine intrinsicfactor. The E. coli cells were lysed and the proteins were resolvedusing SDS-PAGE (Sodium dodecyl sulfate polyacrylamide gelelectrophoresis). Lane 1 contains molecular weight markers (marked inkilodaltons). Lanes 2 and 4 contain samples taken at 0 hourpost-induction (0 HPI). Lanes 3 and 5 contain samples taken at 4 HPI and3 HPI. Lane 6 represents the cellpaste (cells after concentration andcentrifugation). Lane 8 contains the native porcine intrinsic factor(purified from hog (Sus scrofa) gut).

FIG. 2 illustrates the binding of recombinant porcine intrinsic factorto vitamin B₁₂. The E. coli cells were lysed and the proteins wereresolved using SDS-PAGE and blotted onto a nitrocellulose membrane. Themembrane was probed with vitamin B₁₂ conjugate to alkaline phosphatase.Protein bands that bound vitamin B₁₂ were identified by incubation withalkaline phosphatase substrates that develop color. Lane 1 containsmolecular weight markers (marked in kilodaltons). Lanes 2, 3, 4, and 5represent cells from various clones expressing recombinant porcineintrinsic factor. Lane 6 contains the native porcine intrinsic factor(purified from hog (Sus scrofa) gut). The recombinant intrinsic factorprotein band developed color, thereby demonstrating that the intrinsicfactor bound vitamin B₁₂.

FIG. 3 illustrates the binding of recombinant porcine intrinsic factorto anti-intrinsic factor antibody by Western blotting. The E. coli cellswere lysed and the proteins were resolved using SDS-PAGE and blottedonto a nitrocellulose membrane. The membrane was then probed withanti-intrinsic factor antibody. Lane 1 contains molecular weight markers(marked in kilodaltons). Lanes 2, 3, 4, and 5 represent cells fromvarious clones expressing recombinant porcine intrinsic factor. Lane 6contains the native porcine intrinsic factor (purified from hog (Susscrofa) gut). The recombinant intrinsic factor protein band developedcolor, thereby demonstrating that the recombinant intrinsic factor wasrecognized by the antibody.

FIG. 4 illustrates the alignment of the nucleotide sequence of porcineintrinsic factor, human intrinsic factor, rat intrinsic factor, andmouse intrinsic factor.

FIG. 5 illustrates the percent identity between the nucleotide sequencesof porcine intrinsic factor and human intrinsic factor, between thenucleotide sequences of porcine intrinsic factor and rat intrinsicfactor, and between the nucleotide sequences of porcine intrinsic factorand mouse intrinsic factor.

FIG. 6 illustrates the alignment of the putative amino acid sequence ofintrinsic factor encoded by Sus scrofa with known intrinsic factorsequences from human, rat, and mouse.

FIG. 7 illustrates the percent identity between the amino acid sequencesof porcine intrinsic factor and human intrinsic factor, between theamino acid sequences of porcine intrinsic factor and rat intrinsicfactor, and between the amino acid sequences of porcine intrinsic factorand mouse intrinsic factor.

DETAILED DESCRIPTION

For purposes of the present invention, the term “fragment”, with respectto a nucleotide sequence, is defined as a contiguous sequence ofapproximately at least 6, preferably at least about 8, more preferablyat least about 10 nucleotides, and even more preferably at least about15 nucleotides corresponding to a region of the specified nucleotidesequence.

The invention also includes a purified polypeptide which binds vitaminB₁₂ and has at least about 70% amino acid similarity or identity,preferably at least about 80% amino acid similarity or identity and morepreferably at least about 85% amino acid similarity or identity to theamino acid sequences of SEQ ID NO: 3, SEQ ID NO: 6; or SEQ ID NO: 9 ofthe above-noted proteins which are, in turn, encoded by theabove-described nucleotide sequences.

The term “identity” refers to the relatedness of two sequences on anucleotide-by-nucleotide basis over a particular comparison window orsegment. Thus, identity is defined as the degree of sameness,correspondence or equivalence between the same strands (either sense orantisense) of two DNA segments (or two amino acid sequences).“Percentage of sequence identity” is calculated by comparing twooptimally aligned sequences over a particular region, determining thenumber of positions at which the identical base or amino acid occurs inboth sequences in order to yield the number of matched positions,dividing the number of such positions by the total number of positionsin the segment being compared and multiplying the result by 100. Optimalalignment of sequences may be conducted by the algorithm of Smith &Waterman, Appl. Math. 2:482 (1981), by the algorithm of Needleman &Wunsch, J. Mol. Biol. 48:443 (1970), by the method of Pearson & Lipman,Proc. Natl. Acad. Sci. (USA) 85:2444 (1988) and by computer programswhich implement the relevant algorithms (e.g., Clustal Macaw Pileup(http:/cmgm.stanford.edu/biochem218/11Multiple.pdf; Higgins et al.,CABIOS. 5L151-153 (1989)), FASTDB (Intelligenetics), BLAST (NationalCenter for Biomedical Information; Altschul et al., Nucleic AcidsResearch 25:3389-3402 (1997)), PILEUP (Genetics Computer Group, Madison,Wis.) or GAP, BESTFIT, FASTA and TFASTA (Wisconsin Genetics SoftwarePackage Release 7.0, Genetics Computer Group, Madison, Wis.). (See U.S.Pat. No. 5,912,120.)

For purposes of the present invention, the term “complementarity” isdefined as the degree of relatedness between two DNA segments. It isdetermined by measuring the ability of the sense strand of one DNAsegment to hybridize with the anti-sense strand of the other DNAsegment, under appropriate conditions, to form a double helix. The term“complement” is defined as a sequence which pairs to a given sequencebased upon the canonic base-pairing rules. For example, a sequence A-G-Tin one nucleotide strand is “complementary” to T-C-A in the otherstrand.

In the double helix, adenine appears in one strand, thymine appears inthe other strand. Similarly, wherever guanine is found in one strand,cytosine is found in the other. The greater the relatedness between thenucleotide sequences of two DNA segments, the greater the ability toform hybrid duplexes between the strands of the two DNA segments.

The term “similarity”, with respect to two amino acid sequences, isdefined as the presence of a series of identical as well as conservedamino acid residues in both sequences. The higher the degree ofsimilarity between two amino acid sequences, the higher thecorrespondence, sameness or equivalence of the two sequences. (The term“identity”, with respect to two amino acid sequences, is defined as thepresence of a series of exactly alike or invariant amino acid residuesin both sequences.) The definitions of “complementarity”, “identity” and“similarity” are well known to those of ordinary skill in the art.

The phrase “encoded by” refers to a nucleic acid sequence which codesfor a polypeptide sequence, wherein the polypeptide sequence or aportion thereof contains an amino acid sequence of at least 3 aminoacids, more preferably at least 8 amino acids, and even more preferablyat least 15 amino acids from a polypeptide encoded by the nucleic acidsequence.

The present invention also encompasses an isolated nucleotide sequencewhich encodes porcine intrinsic factor and that is hybridizable, undermoderately stringent conditions, to a nucleic acid having a nucleotidesequence comprising or complementary to the nucleotide sequencesdescribed above (see SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO: 7). Anucleic acid molecule is “hybridizable” to another nucleic acid moleculewhen a single-stranded form of the nucleic acid molecule can anneal tothe other nucleic acid molecule under the appropriate conditions oftemperature and ionic strength (see Sambrook et al., “Molecular Cloning:A Laboratory Manual, Second Edition (1989), Cold Spring HarborLaboratory Press, Cold Spring Harbor, N.Y.)). The conditions oftemperature and ionic strength determine the “stringency” of thehybridization.

The term “hybridization” as used herein is generally used to meanhybridization of nucleic acids at appropriate conditions of stringencyas would be readily evident to those skilled in the art depending uponthe nature of the probe sequence and target sequences. Conditions ofhybridization and washing are well known in the art, and the adjustmentof conditions depending upon the desired stringency by varyingincubation time, temperature, and/or ionic strength of the solution arereadily accomplished. See, for example, Sambrook, J. et al., MolecularCloning: A Laboratory Manual, 2nd edition, Cold Spring Harbor Press,Cold Spring Harbor, N.Y., 1989, as noted above and incorporated hereinby reference. (See also Short Protocols in Molecular Biology, ed.Ausubel et al. and Tijssen, Techniques in Biochemistry and MolecularBiology-Hybridization with Nucleic Acid Probes, “Overview of principlesof hybridization and the strategy of nucleic acid assays” (1993), bothincorporated herein by reference.) Specifically, the choice ofconditions is dictated by the length of the sequences being hybridized,in particular, the length of the probe sequence, the relative G-Ccontent of the nucleic acids and the amount of mismatches to bepermitted. Low stringency conditions are preferred when partialhybridization between strands that have lesser degrees ofcomplementarity is desired. When perfect or near perfect complementarityis desired, high stringency conditions are preferred. For typical highstringency conditions, the hybridization solution contains 6×S.S.C.,0.01 M EDTA, 1×Denhardt's solution and 0.5% SDS. Hybridization iscarried out at about 68 degrees Celsius for about 3 to 4 hours forfragments of cloned DNA and for about 12 to about 16 hours for totaleukaryotic DNA. For moderate stringencies, one may utilize filterpre-hybridizing and hybridizing with a solution of 3× sodium chloride,sodium citrate (SSC), 50% formamide (0.1 M of this buffer at pH 7.5) and5×Denhardt's solution. One may then pre-hybridize at 37 degrees Celsiusfor 4 hours, followed by hybridization at 37 degrees Celsius with anamount of labeled probe equal to 3,000,000 cpm total for 16 hours,followed by a wash in 2×SSC and 0.1% SDS solution, a wash of 4 times for1 minute each at room temperature and 4 times at 60 degrees Celsius for30 minutes each. Subsequent to drying, one exposes to film. For lowerstringencies, the temperature of hybridization is reduced to about 12degrees Celsius below the melting temperature (T_(m)) of the duplex. TheT_(m) is known to be a function of the G-C content and duplex length aswell as the ionic strength of the solution.

“Hybridization” requires that two nucleic acids contain complementarysequences. However, depending on the stringency of the hybridization,mismatches between bases may occur. As noted above, the appropriatestringency for hybridizing nucleic acids depends on the length of thenucleic acids and the degree of complementation. Such variables are wellknown in the art. More specifically, the greater the degree ofsimilarity or homology between two nucleotide sequences, the greater thevalue of Tm for hybrids of nucleic acids having those sequences. Forhybrids of greater than 100 nucleotides in length, equations forcalculating Tm have been derived (see Sambrook et al., supra). Forhybridization with shorter nucleic acids, the position of mismatchesbecomes more important, and the length of the oligonucleotide determinesits specificity (see Sambrook et al., supra).

As used herein, the phrase “isolated nucleic acid fragment or sequence”means a polymer of RNA or DNA that is single-stranded ordouble-stranded, optionally containing synthetic, non-natural or alterednucleotide bases. An isolated nucleic acid fragment in the form of apolymer of DNA may be comprised of one or more segments of cDNA, genomicDNA or synthetic DNA. (The term “fragment”, with respect to a specifiedpolynucleotide, refers to a polynucleotide sequence which comprises acontiguous sequence of approximately at least about 6 nucleotides,preferably at least about 8 nucleotides, more preferably at least about10 nucleotides, and even more preferably at least about 15 nucleotides,and most preferable at least about 25 nucleotides identical orcomplementary to a region of the specified nucleotide sequence.)Nucleotides (usually found in their 5′-monophosphate form) are referredto by their single letter designation as follows: “A” for adenylate ordeoxyadenylate (for RNA or DNA, respectively), “C” for cytidylate ordeoxycytidylate, “G” for guanylate or deoxyguanylate, “U” for uridylate,“T” for deoxythymidylate, “R” for purines (A or G), “Y” for pyrimidines(C or T), “K” for G or T, “H” for A or C or T, “I” for inosine, and “N”for any nucleotide.

The phrases “fragment or subfragment that is functionally equivalent”and “functionally equivalent fragment or subfragment” are usedinterchangeably herein. These phrases refer to a portion or subsequenceof an isolated nucleic acid fragment in which the ability to alter geneexpression or produce a certain phenotype is retained whether or not thefragment or subfragment encodes an active enzyme. For example, thefragment or subfragment can be used in the design of chimeric constructsto produce the desired phenotype in a transformed plant. Chimericconstructs can be designed for use in co-suppression or antisense bylinking a nucleic acid fragment or subfragment thereof, whether or notit encodes an active enzyme, in the appropriate orientation relative toa plant promoter sequence.

The terms/phrases “homology”, “homologous”, “substantially similar” and“corresponding substantially” are used interchangeably herein. Theyrefer to nucleic acid fragments wherein changes in one or morenucleotide bases does not affect the ability of the nucleic acidfragment to mediate gene expression or produce a certain phenotype.These terms also refer to modifications of the nucleic acid fragments ofthe instant invention such as deletion or insertion of one or morenucleotides that do not substantially alter the functional properties ofthe resulting nucleic acid fragment relative to the initial, unmodifiedfragment. It is therefore understood, as those skilled in the art willappreciate, that the invention encompasses more than the specificexemplary sequences.

The term “gene” refers to a nucleic acid fragment that expresses aspecific protein, including regulatory sequences preceding (5′non-coding sequences) and following (3′ non-coding sequences) the codingsequence.

The phrase “native gene” refers to a gene as found in nature with itsown regulatory sequences. In contrast, the phrase “chimeric construct”refers to a combination of nucleic acid fragments that are not normallyfound together in nature. Accordingly, a chimeric construct may compriseregulatory sequences and coding sequences that are derived fromdifferent sources, or regulatory sequences and coding sequences derivedfrom the same source, but arranged in a manner different than thatnormally found in nature. (The term “isolated” means that the sequenceis removed from its natural environment.)

The phrase “foreign gene” refers to a gene not normally found in thehost organism, but that is introduced into the host organism by genetransfer. Foreign genes can comprise native genes inserted into anon-native organism, or chimeric constructs. The term “transgene” meansa gene that has been introduced into the genome by a transformationprocedure.

The phrase “coding sequence” refers to a DNA sequence that codes for aspecific amino acid sequence. The term “regulatory sequences” refers tonucleotide sequences located upstream (5′ non-coding sequences), within,or downstream (3′ non-coding sequences) of a coding sequence, and whichinfluence the transcription, RNA processing or stability, or translationof the associated coding sequence. Regulatory sequences may include, butare not limited to, promoters, translation leader sequences, introns,and polyadenylation recognition sequences.

The term “promoter” refers to a DNA sequence capable of controlling theexpression of a coding sequence or functional RNA. The promoter sequenceconsists of proximal and more distal upstream elements, the latterelements often referred to as enhancers. Accordingly, the term“enhancer” means a DNA sequence that can stimulate promoter activity andmay be an innate element of the promoter or a heterologous elementinserted to enhance the level or tissue-specificity of a promoter.Promoter sequences can also be located within the transcribed portionsof genes, and/or downstream of the transcribed sequences. Promoters maybe derived in their entirety from a native gene, or be composed ofdifferent elements derived from different promoters found in nature, oreven comprise synthetic DNA segments. It is understood by those skilledin the art that different promoters may direct the expression of a genein different tissues or cell types, or at different stages ofdevelopment, or in response to different environmental conditions.Promoters that cause a gene to be expressed in most host cell types atmost times are commonly referred to as “constitutive promoters”. It isfurther recognized that since in most cases the exact boundaries ofregulatory sequences have not been completely defined, DNA fragments ofsome variation may have identical promoter activity.

The term “intron” means an intervening sequence in a gene that does notencode a portion of the protein sequence. Thus, such sequences aretranscribed into RNA but are then excised and are not translated. Theterm is also used for the excised RNA sequences. The term “exon” means aportion of the gene sequence that is transcribed and is found in themature messenger RNA derived from the gene, but is not necessarily apart of the sequence that encodes the final gene product.

The phrase “translation leader sequence” refers to a DNA sequencelocated between the promoter sequence of a gene and the coding sequence.The translation leader sequence is present in the fully processed mRNAupstream of the translation start sequence. The translation leadersequence may affect processing of the primary transcript to mRNA, mRNAstability or translation efficiency. Examples of translation leadersequences have been described (Turner, R. and Foster, G. D. (1995)Molecular Biotechnology 3:225).

The phrase “3′ non-coding sequences” refers to DNA sequences locateddownstream of a coding sequence and include polyadenylation recognitionsequences and other sequences encoding regulatory signals capable ofaffecting mRNA processing or gene expression. The polyadenylation signalis usually characterized by affecting the addition of polyadenylic acidtracts to the 3′ end of the mRNA precursor. The use of different 3′non-coding sequences is exemplified by Ingelbrecht et al., Plant Cell1:671-680 (1989).

The phrase “RNA transcript” refers to the product resulting from RNApolymerase-catalyzed transcription of a DNA sequence. When the RNAtranscript is a perfect complementary copy of the DNA sequence, it isreferred to as the primary transcript or it may be a RNA sequencederived from post-transcriptional processing of the primary transcriptand is referred to as the mature RNA. The phrase “messenger RNA (mRNA)”refers to the RNA that is without introns and that can be translatedinto protein by the cell. The term “cDNA” refers to a DNA that iscomplementary to and synthesized from a mRNA template using the enzymereverse transcriptase. The cDNA can be single-stranded or converted intothe double-stranded form using the Klenow fragment of DNA polymerase I.The phrase “sense RNA” refers to RNA transcript that includes the mRNAand can be translated into protein within a cell or in vitro.

The phrase “antisense RNA” refers to an RNA transcript that iscomplementary to all or part of a target primary transcript or mRNA andthat blocks the expression of a target gene (U.S. Pat. No. 5,107,065).The complementarity of an antisense RNA may be with any part of thespecific gene transcript, i.e., at the 5′ non-coding sequence, 3′non-coding sequence, introns, or the coding sequence. The phrase“functional RNA” refers to antisense RNA, ribozyme RNA, or other RNAthat may not be translated but yet has an effect on cellular processes.The term “complement” and the phrase “reverse complement” are usedinterchangeably herein with respect to mRNA transcripts, and are meantto define the antisense RNA of the message.

The phrase “endogenous RNA” refers to any RNA which is encoded by anynucleic acid sequence present in the genome of the host prior totransformation with the recombinant construct of the present invention,whether naturally-occurring or non-naturally occurring, i.e., introducedby recombinant means, mutagenesis, etc.

The phrase “non-naturally occurring” means artificial, not consistentwith what is normally found in nature.

The phrase “operably linked” refers to the association of nucleic acidsequences on a single nucleic acid fragment so that the function of oneis regulated by the other. For example, a promoter is operably linkedwith a coding sequence when it is capable of regulating the expressionof that coding sequence (i.e., that the coding sequence is under thetranscriptional control of the promoter). Coding sequences can beoperably linked to regulatory sequences in a sense or antisenseorientation. In another example, the complementary RNA regions of theinvention can be operably linked, either directly or indirectly, 5′ tothe target mRNA, or 3′ to the target mRNA, or within the target mRNA, ora first complementary region is 5′ and its complement is 3′ to thetarget mRNA. “Operably linked” sequences include both expression controlsequences that are contiguous with the gene of interest and expressioncontrol sequences that act in trans or at a distance to control the geneof interest. The phrase “expression control sequence” as used hereinrefers to polynucleotide sequences which are necessary to effect theexpression and processing of coding sequences to which they are ligated.Expression control sequences include appropriate transcriptioninitiation, termination, promoter and enhancer sequences; efficient RNAprocessing signals such as splicing and polyadenylation signals;sequences that stabilize cytoplasmic mRNA; sequences that enhancetranslation efficiency (i.e., Kozak consensus sequence); sequences thatenhance protein stability; and when desired, sequences that enhanceprotein secretion. The nature of such control sequences differsdepending upon the host organism; in prokaryotes, such control sequencesgenerally include promoter, ribosomal binding site, and transcriptiontermination sequence; in eukaryotes, generally, such control sequencesinclude promoters and transcription termination sequence. The phrase“control sequences” is intended to include components whose presence isessential for expression and processing, and can also include additionalcomponents whose presence is advantageous, for example, leader sequencesand fusion partner sequences.

The term “expression”, as used herein, refers to the production of afunctional end-product. Expression of a gene involves transcription ofthe gene and translation of the mRNA into a precursor or mature protein.

“Antisense inhibition” refers to the production of antisense RNAtranscripts capable of suppressing the expression of the target protein.The term “co-suppression” refers to the production of sense RNAtranscripts capable of suppressing the expression of identical orsubstantially similar foreign or endogenous genes (U.S. Pat. No.5,231,020).

The phrase “mature protein” refers to a post-translationally processedpolypeptide; i.e., one from which any pre- or propeptides present in theprimary translation product have been removed. The term “precursor”protein refers to the primary product of translation of mRNA; i.e., withpre- and pro-peptides still present. Pre- and pro-peptides may be butare not limited to intracellular localization signals.

The term “transformation”, as defined herein, refers to any process bywhich exogenous DNA enters a host cell. Transformation may occur undernatural or artificial conditions using various methods well known in theart. Transformation may rely on any known method for the insertion offoreign nucleic acid sequences into a prokaryotic or eukaryotic hostcell. The method is selected based on the host cell being transformedand may include, but is not limited to, viral infection,electroporation, lipofection, and particle bombardment. Such“transformed” cells include stably transformed cells in which theinserted DNA is capable of replication either as an autonomouslyreplicating plasmid or as part of the host chromosome. They also includecells that transiently express the inserted DNA or RNA for limitedperiods of time.

The phrase “stable transformation” refers to the transfer of a nucleicacid fragment into a genome of a host organism, resulting in geneticallystable inheritance. In contrast, the phrase “transient transformation”refers to the transfer of a nucleic acid fragment into the nucleus, orDNA-containing organelle, of a host organism resulting in geneexpression without integration or stable inheritance. Host organismscontaining the transformed nucleic acid fragments are referred to as“transgenic” organisms. The preferred method of cell transformation ofrice, corn and other monocots is the use of particle-accelerated or“gene gun” transformation technology (Klein et al., (1987) Nature(London) 327:70-73; U.S. Pat. No. 4,945,050), or anAgrobacterium-mediated method using an appropriate Ti plasmid containingthe transgene (Ishida Y. et al., 1996, Nature Biotech. 14:745-750). Theterm “transformation” as used herein refers to both stabletransformation and transient transformation.

Standard recombinant DNA and molecular cloning techniques used hereinare well known in the art and are described more fully in Sambrook, J.,Fritsch, E. F. and Maniatis, T., Molecular Cloning: A Laboratory Manual;Cold Spring Harbor Laboratory Press: Cold Spring Harbor, 1989(hereinafter “Sambrook”).

The term “recombinant” refers to an artificial combination of twootherwise separated segments of sequence, e.g., by chemical synthesis orby the manipulation of isolated segments of nucleic acids by geneticengineering techniques.

The term “PCR” and the phrase “Polymerase Chain Reaction” refers to atechnique for the synthesis of large quantities of specific DNAsegments, consists of a series of repetitive cycles (Perkin Elmer CetusInstruments, Norwalk, Conn.). Typically, the double stranded DNA is heatdenatured, the two primers complementary to the 3′ boundaries of thetarget segment are annealed at low temperature and then extended at anintermediate temperature. One set of these three consecutive steps isreferred to as a cycle.

Polymerase chain reaction (“PCR”) is a powerful technique used toamplify DNA millions of fold, by repeated replication of a template, ina short period of time. (Mullis et al., Cold Spring Harbor Symp. Quant.Biol. 51:263-273 (1986); Erlich et al., European Patent Application No.50,424; European Patent Application No. 84,796; European PatentApplication No. 258,017; European Patent Application No. 237,362;Mullis, European Patent Application No. 201,184; Mullis et al., U.S.Pat. No. 4,683,202; Erlich, U.S. Pat. No. 4,582,788; and Saiki et al.,U.S. Pat. No. 4,683,194). The process utilizes sets of specific in vitrosynthesized oligonucleotides to prime DNA synthesis. The design of theprimers is dependent upon the sequences of DNA that are desired to beanalyzed. The technique is carried out through many cycles (usually20-50) of melting the template at high temperature, allowing the primersto anneal to complementary sequences within the template and thenreplicating the template with DNA polymerase.

The products of PCR reactions are analyzed by separation in agarose gelsfollowed by ethidium bromide staining and visualization with UVtransillumination. Alternatively, radioactive dNTPs can be added to thePCR in order to incorporate label into the products. In this case theproducts of PCR are visualized by exposure of the gel to x-ray film. Theadded advantage of radiolabeling PCR products is that the levels ofindividual amplification products can be quantitated.

The term “RT-PCR” means a combination of Reverse Transcription and PCR.Reverse transcription is a process where RNA is used as a startingmaterial to make DNA using an enzyme called Reverse Transcriptase. Thefirst strand of DNA that is made during reverse transcription is used asthe starting material for the PCR reactions that follow.

The phrases “recombinant construct”, “expression construct” and“recombinant expression construct” are used interchangeably herein.These phrases refer to a functional unit of genetic material that can beinserted into the genome of a cell using standard methodology well knownto one skilled in the art. Such construct may be itself or may be usedin conjunction with a vector. If a vector is used then the choice ofvector is dependent upon the method that will be used to transform hostplants as is well known to those skilled in the art. For example, aplasmid vector can be used. The skilled artisan is well aware of thegenetic elements that must be present on the vector in order tosuccessfully transform, select and propagate host cells comprising anyof the isolated nucleic acid fragments of the invention. The skilledartisan will also recognize that different independent transformationevents will result in different levels and patterns of expression (Joneset al., (1985) EMBO J. 4:2411-2418; De Almeida et al., (1989) Mol. Gen.Genetics 218:78-86), and thus that multiple events must be screened inorder to obtain lines displaying the desired expression level andpattern. Such screening may be accomplished by Southern analysis of DNA,Northern analysis of mRNA expression, Western analysis of proteinexpression, or phenotypic analysis.

The term “polypeptide” as used herein, refers to any polymeric chain ofamino acids. The terms “peptide” and “protein” are used interchangeablywith the term polypeptide and also refer to a polymeric chain of aminoacids. The term “polypeptide” encompasses native or artificial proteins,protein fragments and polypeptide analogs of a protein sequence. Apolypeptide may be monomeric or polymeric.

The phrases “isolated protein” and “isolated polypeptide” refer to aprotein or polypeptide that by virtue of its origin or source ofderivation is not associated with naturally associated components thataccompany it in its native state; is substantially free of otherproteins from the same species; is expressed by a cell from a differentspecies; or does not occur in nature. Thus, a polypeptide that ischemically synthesized or synthesized in a cellular system differentfrom the cell from which it naturally originates will be “isolated” fromits naturally associated components. A protein may also be renderedsubstantially free of naturally associated components by isolation,using protein purification techniques well known in the art.

The phrases “specific binding” and “specifically binding”, as usedherein, in reference to the interaction of an antibody, a protein, or apeptide with a second chemical species, mean that the interaction isdependent upon the presence of a particular structure (e.g., anantigenic determinant or epitope) on the chemical species; for example,an antibody recognizes and binds to a specific protein structure ratherthan to proteins generally. If an antibody is specific for epitope “A”,the presence of a molecule containing epitope A (or free, unlabeled A),in a reaction containing labeled “A” and the antibody, will reduce theamount of labeled A bound to the antibody.

The term “antibody”, as used herein, broadly refers to anyimmunoglobulin (Ig) molecule comprised of four polypeptide chains, twoheavy (H) chains and two light (L) chains, or any functional fragment,mutant, variant, or derivation thereof, which retains the essentialepitope binding features of an Ig molecule. Such mutant, variant, orderivative antibody formats are known in the art, non-limitingembodiments of which are discussed below.

In a full-length antibody, each heavy chain is comprised of a heavychain variable region (abbreviated herein as HCVR or VH) and a heavychain constant region. The heavy chain constant region is comprised ofthree domains, CH1, CH2 and CH3. Each light chain is comprised of alight chain variable region (abbreviated herein as LCVR or VL) and alight chain constant region. The light chain constant region iscomprised of one domain, CL. The VH and VL regions can be furthersubdivided into regions of hypervariability, termed complementaritydetermining regions (CDR), interspersed with regions that are moreconserved, termed framework regions (FR). Each VH and VL is composed ofthree CDRs and four FRs, arranged from amino-terminus tocarboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3,CDR3, FR4.

The phrase “antigen-binding portion” of an antibody (or simply “antibodyportion”), as used herein, refers to one or more fragments of anantibody that retain the ability to specifically bind to an antigen(e.g., hIL-18). It has been shown that the antigen-binding function ofan antibody can be performed by fragments of a full-length antibody.Such antibody embodiments may also be bispecific, dual specific, ormulti-specific formats; specifically binding to two or more differentantigens. Examples of binding fragments encompassed within the phrase“antigen-binding portion” of an antibody include (i) a Fab fragment, amonovalent fragment consisting of the VL, VH, CL and CH1 domains; (ii) aF(ab′)₂ fragment, a bivalent fragment comprising two Fab fragmentslinked by a disulfide bridge at the hinge region; (iii) a Fd fragmentconsisting of the VH and CH1 domains; (iv) a Fv fragment consisting ofthe VL and VH domains of a single arm of an antibody, (v) a dAb fragment(Ward et al., (1989) Nature 341:544-546), which comprises a singlevariable domain; and (vi) an isolated complementarity determining region(CDR). Furthermore, although the two domains of the Fv fragment, VL andVH, are coded for by separate genes, they can be joined, usingrecombinant methods, by a synthetic linker that enables them to be madeas a single protein chain in which the VL and VH regions pair to formmonovalent molecules (known as single chain Fv (scFv); see e.g., Bird etal. (1988) Science 242:423-426; and Huston et al. (1988) Proc. Natl.Acad. Sci. USA 85:5879-5883). Such single chain antibodies are alsointended to be encompassed within the phrase “antigen-binding portion”of an antibody. Other forms of single chain antibodies, such asdiabodies are also encompassed. Diabodies are bivalent, bispecificantibodies in which VH and VL domains are expressed on a singlepolypeptide chain, but using a linker that is too short to allow forpairing between the two domains on the same chain, thereby forcing thedomains to pair with complementary domains of another chain and creatingtwo antigen binding sites (see e.g., Holliger, P., et al. (1993) Proc.Natl. Acad. Sci. USA 90:6444-6448; Poljak, R. J., et al. (1994)Structure 2:1121-1123). Such antibody binding portions are known in theart (Kontermann and Dubel eds., Antibody Engineering (2001)Springer-Verlag. New York. 790 pp. (ISBN 3-54041354-5).

Still further, an antibody or antigen-binding portion thereof may bepart of a larger immunoadhesion molecules, formed by covalent ornoncovalent association of the antibody or antibody portion with one ormore other proteins or peptides. Examples of such immunoadhesionmolecules include use of the streptavidin core region to make atetrameric scFv molecule (Kipriyanov, S. M., et al. (1995) HumanAntibodies and Hybridomas 6:93-101) and use of a cysteine residue, amarker peptide and a C-terminal polyhistidine tag to make bivalent andbiotinylated scFv molecules (Kipriyanov, S. M., et al. (1994) Mol.Immunol. 31:1047-1058). Antibody portions, such as Fab and F(ab′)₂fragments, can be prepared from whole antibodies using conventionaltechniques, such as papain or pepsin digestion, respectively, of wholeantibodies. Moreover, antibodies, antibody portions and immunoadhesionmolecules can be obtained using standard recombinant DNA techniques, asdescribed herein.

The phrase “isolated antibody”, as used herein, is intended to refer toan antibody that is substantially free of other antibodies havingdifferent antigenic specificities (e.g., an isolated antibody thatspecifically binds hIL-18 is substantially free of antibodies thatspecifically bind antigens other than hIL-18). An isolated antibody thatspecifically binds hIL-18 may, however, have cross-reactivity to otherantigens, such as IL-18 molecules from other species. Moreover, anisolated antibody may be substantially free of other cellular materialand/or chemicals.

A “monoclonal antibody” as used herein is intended to refer to apreparation of antibody molecules which share a common heavy chain andcommon light chain amino acid sequence, in contrast with “polyclonal”antibody preparations which contain a mixture of different antibodies.Monoclonal antibodies can be generated by several novel technologieslike phage, bacteria, yeast or ribosomal display, as well as classicalmethods exemplified by hybridoma-derived antibodies (e.g., an antibodysecreted by a hybridoma prepared by hybridoma technology, such as thestandard Kohler and Milstein hybridoma methodology ((1975) Nature256:495-497). Thus, a non-hybridoma-derived antibody of the invention isstill referred to as a monoclonal antibody although it may have beenderived by non-classical methodologies.

The phrase “recombinant antibody” refers to antibodies that areprepared, expressed, created or isolated by recombinant means, such asantibodies expressed using a recombinant expression vector transfectedinto a host cell, antibodies isolated from a recombinant, combinatorialantibody library, antibodies isolated from an animal (e.g., a mouse)that is transgenic for human immunoglobulin genes (see, e.g., Taylor etal. (1992) Nucleic Acids Research 20:6287-6295) or antibodies prepared,expressed, created or isolated by any other means that involves splicingof particular immunoglobulin gene sequences (such as humanimmunoglobulin gene sequences) to other DNA sequences. Examples ofrecombinant antibodies include chimeric, CDR-grafted and humanizedantibodies.

The phrase “human antibody”, as used herein, is intended to includeantibodies having variable and constant regions derived from humangermline immunoglobulin sequences. The human antibodies of the inventionmay include amino acid residues not encoded by human germlineimmunoglobulin sequences (e.g., mutations introduced by random orsite-specific mutagenesis in vitro or by somatic mutation in vivo), forexample in the CDRs and in particular CDR3. However, the phrase “humanantibody”, as used herein, is not intended to include antibodies inwhich CDR sequences derived from the germline of another mammalianspecies, such as a mouse, have been grafted onto human frameworksequences.

The phrase “recombinant human antibody”, as used herein, is intended toinclude all human antibodies that are prepared, expressed, created orisolated by recombinant means, such as antibodies expressed using arecombinant expression vector transfected into a host cell, antibodiesisolated from a recombinant, combinatorial human antibody library(Hoogenboom H. R., (1997) TIB Tech. 15:62-70; Azzazy H., and HighsmithW. E., (2002) Clin. Biochem. 35:425-445; Gavilondo J. V., and Larrick J.W. (2002) BioTechniques 29:128-145; Hoogenboom H., and Chames P. (2000)Immunology Today 21:371-378), antibodies isolated from an animal (e.g.,a mouse) that is transgenic for human immunoglobulin genes (see e.g.,Taylor, L. D., et al. (1992) Nucl. Acids Res. 20:6287-6295; KellermannS-A., and Green L. L. (2002) Current Opinion in Biotechnology13:593-597; Little M. et al (2000) Immunology Today 21:364-370) orantibodies prepared, expressed, created or isolated by any other meansthat involves splicing of human immunoglobulin gene sequences to otherDNA sequences. Such recombinant human antibodies have variable andconstant regions derived from human germline immunoglobulin sequences.In certain embodiments, however, such recombinant human antibodies aresubjected to in vitro mutagenesis (or, when an animal transgenic forhuman Ig sequences is used, in vivo somatic mutagenesis) and thus theamino acid sequences of the VH and VL regions of the recombinantantibodies are sequences that, while derived from and related to humangermline VH and VL sequences, may not naturally exist within the humanantibody germine repertoire in vivo.

The phrase “chimeric antibody” refers to antibodies which comprise heavyand light chain variable region sequences from one species and constantregion sequences from another species, such as antibodies having murineheavy and light chain variable regions linked to human constant regions.

The phrase “CDR-grafted antibody” refers to antibodies which compriseheavy and light chain variable region sequences from one species but inwhich the sequences of one or more of the CDR regions of V_(H) and/or VLare replaced with CDR sequences of another species, such as antibodieshaving murine heavy and light chain variable regions in which one ormore of the murine CDRs (e.g., CDR3) has been replaced with human CDRsequences.

The phrase “humanized antibody” refers to antibodies which compriseheavy and light chain variable region sequences from a non-human species(e.g., a mouse) but in which at least a portion of the VH and/or VLsequence has been altered to be more “human-like”, i.e., more similar tohuman germline variable sequences. One type of humanized antibody is aCDR-grafted antibody, in which human CDR sequences are introduced intonon-human VH and VL sequences to replace the corresponding nonhuman CDRsequences.

The term “epitope” includes any polypeptide determinant capable ofspecific binding to an immunoglobulin or T-cell receptor. In certainembodiments, epitope determinants include chemically active surfacegroupings of molecules such as amino acids, sugar side chains,phosphoryl, or sulfonyl, and, in certain embodiments, may have specificthree dimensional structural characteristics, and/or specific chargecharacteristics. An epitope is a region of an antigen that is bound byan antibody. In certain embodiments, an antibody is said to specificallybind an antigen when it preferentially recognizes its target antigen ina complex mixture of proteins and/or macromolecules.

The phrase “crystallized binding protein” as used herein, refers to apolypeptide that exists in the form of a crystal. Crystals are one formof the solid state of matter, which is distinct from other forms such asthe amorphous solid state or the liquid crystalline state. Crystals arecomposed of regular, repeating, three-dimensional arrays of atoms, ions,molecules (e.g., proteins such as antibodies), or molecular assemblies(e.g., antigen/antibody complexes). These three-dimensional arrays arearranged according to specific mathematical relationships that arewell-understood in the field. The fundamental unit, or building block,that is repeated in a crystal is called the asymmetric unit. Repetitionof the asymmetric unit in an arrangement that conforms to a given,well-defined crystallographic symmetry provides the “unit cell” of thecrystal. Repetition of the unit cell by regular translations in allthree dimensions provides the crystal. See Giege, R. and Ducruix, A.Barrett, Crystallization of Nucleic Acids and Proteins, a PracticalApproach, 2nd ea., pp. 20 1-16, Oxford University Press, New York, N.Y.,(1999).”

The term “polynucleotide” as referred to herein means a polymeric formof two or more nucleotides, either ribonucleotides or deoxynucleotidesor a modified form of either type of nucleotide. The term includessingle and double stranded forms of DNA but preferably isdouble-stranded DNA.

The phrase “isolated polynucleotide” as used herein means apolynucleotide (e.g., of genomic, cDNA, or synthetic origin, or somecombination thereof) that, by virtue of its origin, the “isolatedpolynucleotide” is not associated with all or a portion of apolynucleotide with which the “isolated polynucleotide” is found innature; is operably linked to a polynucleotide that it is not linked toin nature; or does not occur in nature as part of a larger sequence.

The term “vector”, as used herein, is intended to refer to a nucleicacid molecule capable of transporting another nucleic acid to which ithas been linked. One type of vector is a “plasmid”, which term refers toa circular double stranded DNA loop into which additional DNA segmentsmay be ligated. Another type of vector is a viral vector, whereinadditional DNA segments may be ligated into the viral genome. Certainvectors are capable of autonomous replication in a host cell into whichthey are introduced (e.g., bacterial vectors having a bacterial originof replication and episomal mammalian vectors). Other vectors (e.g.,non-episomal mammalian vectors) can be integrated into the genome of ahost cell upon introduction into the host cell, and thereby arereplicated along with the host genome. Moreover, certain vectors arecapable of directing the expression of genes to which they areoperatively linked. Such vectors are referred to herein as “recombinantexpression vectors” (or simply, “expression vectors”). In general,expression vectors of utility in recombinant DNA techniques are often inthe form of plasmids. In the present specification, the terms “plasmid”and “vector” may be used interchangeably, as the plasmid is the mostcommonly used form of vector. However, the invention is intended toinclude such other forms of expression vectors, such as viral vectors(e.g., replication defective retroviruses, adenoviruses andadeno-associated viruses), which serve equivalent functions.

The phrase “recombinant host cell” (or simply “host cell”), as usedherein, is intended to refer to a cell into which exogenous DNA has beenintroduced. It should be understood that such phrases are intended torefer not only to the particular subject cell, but, to the progeny ofsuch a cell. Because certain modifications may occur in succeedinggenerations due to either mutation or environmental influences, suchprogeny may not, in fact, be identical to the parent cell, but are stillincluded within the scope of the phrase “host cell” as used herein.Preferably host cells include prokaryotic and eukaryotic cells selectedfrom any of the Kingdoms of life. Preferred eukaryotic cells includeprotist, fungal, plant and animal cells. Most preferably host cellsinclude but are not limited to the prokaryotic cell line E. Coli;mammalian cell lines CHO and COS; the insect cell line Sf9; and thefungal cell Saccharomyces cerevisiae.

Standard techniques may be used for recombinant DNA, oligonucleotidesynthesis, and tissue culture and transformation (e.g., electroporation,lipofection). Enzymatic reactions and purification techniques may beperformed according to manufacturer's specifications or as commonlyaccomplished in the art or as described herein. The foregoing techniquesand procedures may be generally performed according to conventionalmethods well known in the art and as described in various general andmore specific references that are cited and discussed throughout thepresent specification. See e.g., Sambrook et al. Molecular Cloning: ALaboratory Manual (2d ed., Cold Spring Harbor Laboratory Press, ColdSpring Harbor, N.Y. (1989)), which is incorporated herein by referencefor any purpose.

The term “primer” means an oligonucleotide or a short single-strandednucleic acid molecule that binds to the DNA sequence of interest andacts as a starting point for the synthesis of nucleic acids from the DNAsequence of interest.

The term “sample”, as used herein, is used in its broadest sense. A“biological sample”, as used herein, includes, but is not limited to,any quantity of a substance from a living thing or formerly livingthing. Such living things include, but are not limited to, humans, mice,rats, monkeys, dogs, rabbits and other animals. Such substances include,but are not limited to, blood, serum, urine, synovial fluid, cells,organs, tissues, bone marrow, lymph nodes and spleen.

This invention relates to the porcine intrinsic factor protein, to thenucleic acid molecules encoding porcine intrinsic factor, to antibodiesraised against porcine intrinsic factor, and to inhibitory compoundsthat regulate porcine intrinsic factor. This invention also providesmethods for identifying and obtaining the protein porcine intrinsicfactor, the nucleic acid molecule of porcine intrinsic factor, andantibodies to the porcine intrinsic factor and portions of thoseantibodies. This invention also demonstrates the use of this protein indiagnostic assays.

The method for producing the porcine intrinsic factor of this inventioninvolves the following steps:

-   -   (a) isolating total RNA from porcine stomach tissue;    -   (b) cloning cDNA encoding porcine intrinsic factor by RT-PCR;    -   (c) inserting porcine intrinsic factor cDNA into an expression        vector;    -   (d) expressing the recombinant intrinsic factor protein in a        host cell system for a period of time and under conditions        suitable for expression of the protein; and    -   (e) purifying the intrinsic factor protein.        The invention also involves checking for the binding activity of        intrinsic factor to vitamin B₁₂. The invention further involves        testing the feasibility of using recombinant intrinsic factor in        automated immunoassay analyzer.

The recombinant porcine intrinsic factor of this invention can be usedin diagnostic assays to detect the levels of vitamin B₁₂ in biologicalsamples.

The Vitamin B₁₂ Diagnostic Assay is part of the menu in platforms fordiagnostic analyzers having such trademarks “IMx”, “AxSYM” and“ARCHITECT”, all of which are commercially available from AbbottLaboratories, Abbott Park, Ill. The intended use of the assay is for thequantitative determination of the vitamin B₁₂ in human serum and plasma.The vitamin B₁₂ assay for the “IMx” and “AxSYM” analyzers is based onthe Microparticle Enzyme Immunoassay (MEIA) technology. The vitamin B₁₂assay for the “ARCHITECT” analyzer is a Chemiluminescent MicroparticleImmunoassay (CMIA).

Intrinsic factor is produced in the stomach. It binds to vitamin B₁₂ inthe proximal small intestine, thereby forming a complex with vitaminB₁₂. This intact complex moves through the intestine until reaches thedistal ileum, where it binds to high-affinity receptors, specific forintrinsic factor, located on the luminal surface of ileal absorptivecells (enterocytes). The intrinsic factor—vitamin B₁₂ complex attachesto these surface receptors rapidly, enters these cells, and finallyreaches the portal circulation. Thus, the intrinsic factor helps in thetransport and absorption of vitamin B₁₂ in the intestine. The ability ofthe intrinsic factor to specifically bind vitamin B₁₂ is used as thepremise in the diagnostic assays developed at Abbott Laboratories,Abbott Park, Ill. The level of vitamin B₁₂ in a biological sample isdeterminative of how much vitamin B₁₂ is bound to particles coated withintrinsic factor.

The percent identity between the nucleotide sequence of porcineintrinsic factor and human intrinsic factor is 83% (see FIGS. 4 and 5).The percent identity between the nucleotide sequence of porcineintrinsic factor and mouse intrinsic factor is 79% (see FIGS. 4 and 5).The percent identity between the nucleotide sequence of porcineintrinsic factor and rat intrinsic factor is 79% (see FIGS. 4 and 5).The percent identity between the amino acid sequence of porcineintrinsic factor and human intrinsic factor is 81% (see FIGS. 6 and 7).The percent identity between the amino acid sequence of porcineintrinsic factor and mouse intrinsic factor is 73% (see FIGS. 6 and 7).The percent identity between the amino acid sequence of porcineintrinsic is factor and rat intrinsic factor is 72% (see FIGS. 6 and 7).

Production of the Recombinant Porcine Intrinsic Factor

Once the gene encoding the porcine intrinsic factor has been isolated,it may then be introduced into either a prokaryotic or eukaryotic hostcell through the use of a vector or construct. The vector, for example,a bacteriophage, cosmid or plasmid, may comprise the nucleotide sequenceencoding the porcine intrinsic factor, as well as any regulatorysequence (e.g., promoter) which is functional in the host cell and isable to elicit expression of the porcine intrinsic factor encoded by thenucleotide sequence. The regulatory sequence (e.g., promoter) is inoperable association with, or operably linked to, the nucleotidesequence. (A promoter is said to be “operably linked” with a codingsequence if the promoter affects transcription or expression of thecoding sequence.) Suitable promoters include, for example, those fromgenes encoding alcohol dehydrogenase, glyceraldehyde-3-phosphatedehydrogenase, phosphoglucoisomerase, phosphoglycerate kinase, acidphosphatase, T7, TPI, lactase, metallothionein, cytomegalovirusimmediate early, whey acidic protein, glucoamylase, and promotersactivated in the presence of galactose, for example, GAL1 and GAL10.Additionally, nucleotide sequences which encode other proteins,oligosaccharides, lipids, etc. may also be included within the vector aswell as other regulatory sequences such as a polyadenylation signal(e.g., the poly-A signal of SV-40T-antigen, ovalalbumin or bovine growthhormone). The choice of sequences present in the construct is dependentupon the desired expression products as well as the nature of the hostcell.

As noted above, once the vector has been constructed, it may then beintroduced into the host cell of choice by methods known to those ofordinary skill in the art including, for example, transfection,transformation and electroporation (see Molecular Cloning: A LaboratoryManual, 2^(nd) ed., Vol. 1-3, ed. Sambrook et al., Cold Spring HarborLaboratory Press (1989)). The host cell is then cultured under suitableconditions permitting expression of the genes leading to the productionof the desired porcine intrinsic factor, which is then recovered andpurified.

Examples of suitable prokaryotic host cells include, for example,bacteria such as Escherichia coli, Bacillus subtilis as well asCyanobacteria such as Spirulina spp. (i.e., blue-green algae). Examplesof suitable eukaryotic host cells include, for example, mammalian cells,plant cells, yeast cells such as Saccharomyces cerevisiae, Saccharomycescarlsbergensis, Lipomyces starkey, Candida spp. such as Yarrowia(Candida) lipolytica, Kluyveromyces spp., Pichia spp., Trichoderma spp.or Hansenula spp., or fungal cells such as filamentous fungal cells, forexample, Aspergillus, Neurospora and Penicillium. Preferably,Saccharomyces cerevisiae (baker's yeast) cells are utilized.

Expression in a host cell can be accomplished in a transient or stablefashion. Transient expression can occur from introduced constructs whichcontain expression signals functional in the host cell, but whichconstructs do not replicate and rarely integrate in the host cell, orwhen the host cell is not proliferating. Transient expression also canbe accomplished by inducing the activity of a regulatable promoteroperably linked to the gene of interest, although such inducible systemsfrequently exhibit a low basal level of expression. Stable expressioncan be achieved by introduction of a construct that can integrate intothe host genome or that autonomously replicates in the host cell. Stableexpression of the gene of interest can be selected through the use of aselectable marker located on or transfected with the expressionconstruct, followed by selection for cells expressing the marker. Whenstable expression results from integration, the site of the construct'sintegration can occur randomly within the host genome or can be targetedthrough the use of constructs containing regions of homology with thehost genome sufficient to target recombination with the host locus.Where constructs are targeted to an endogenous locus, all or some of thetranscriptional and translational regulatory regions can be provided bythe endogenous locus.

To prepare an antibody of the invention, the antibody is raised againstan antigen (i.e., the porcine intrinsic factor or fragment thereof)capable of eliciting production of the antibody. The present inventionincludes the isolated antibody or antibodies raised against the antigen,as well as antibody portions or fragments thereof. Further, theantibodies of the invention include monoclonal and recombinantantibodies, and portions or fragments thereof. In various embodiments,the antibody, or portion thereof, may comprise amino acid sequencesderived entirely from a single species, such as a fully human or fullymouse antibody, or portion thereof. In other embodiments, the antibody,or portion thereof, may be a chimeric antibody or a CDR-grafted antibody(CDR, complementary determining region) or other form of humanizedantibody.

Isolation of the nucleic acid molecule of the present invention wasunexpected because initial attempts to obtain nucleic acid moleculesusing RT-PCR were unsuccessful. After numerous attempts (i.e., a totalof 10 attempts), specific primers that were useful for isolating suchnucleic acid molecules were discovered. The cDNA sequence of the porcineintrinsic factor that can be used to produce recombinant intrinsicfactor protein is now known. This recombinant protein can be used indiagnostic assays to detect levels of vitamin B₁₂ in biological samples(blood, plasma) of patients.

The following non-limiting examples further illustrate this invention.

Example I Cloning of Porcine Intrinsic Factor

Porcine intrinsic factor was produced by the parietal cells of theporcine stomach. Because the parietal cells are highly concentrated inthe fundic region of the stomach, the fundic region was used for totalRNA isolation. The stomach tissue stored in “RNA Later” solution(purchased from Ambion, Inc., Austin, Tex.) was homogenized in “TRIzol”reagent (purchased from Invitrogen, Carlsbad, Calif.), and total RNA wasisolated using the protocol recommended by the vendor. The total RNAisolated from the porcine stomach was used as the starting material inthe Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) reactions.The designs of the primers for RT-PCR were based on the known homologybetween human, mouse, and rat intrinsic factor. The first six RT-PCRruns, each of which involved different reaction conditions, failed toproduce the porcine intrinsic factor cDNA. Additional primers (i.e., atotal of 8 primers) were made and were used in all possible combinationsin the seventh RT-PCR run. In this seventh RT-PCR run, a porcineintrinsic factor cDNA fragment, referred to herein as Porcine IFcDNA₂₀₀₋₁₂₅₄ (1054 bp in length, SEQ ID NO: 1, its reverse complementSEQ ID NO: 2, and its amino acid sequence SEQ ID NO: 3), was obtainedusing the Forward Primer huIF200For (SEQ ID NO: 10) and Reverse PrimerhuIF Reverse 1 (SEQ ID NO: 11). The RT-PCR profile was as follows: RTstep was performed at a temperature of 42° C. for 25 minutes. This stepwas followed by the PCR step, which included one initial denaturationstep at a temperature of 94° C. for 30 seconds; then 40 cycles of thefollowing conditions: a temperature of 94° C. for 30 seconds, then atemperature of 57° C. for 30 seconds, then a temperature of 72° C. for 1minute; followed by a final extension at a temperature of 72° C. for 5minutes. To obtain full-length porcine intrinsic factor cDNA, additionalprimers (i.e., a total of 9 primers) were made, and RT-PCR runs wereperformed. The first four RT-PCR runs, each of which involved differentreaction conditions, failed to produce the porcine intrinsic factorcDNA. In the fifth RT-PCR run, a porcine intrinsic factor cDNA fragment(1234 bp in length), referred to herein as Porcine IF cDNA₁₄₋₁₂₄₈, wasobtained using Forward Primer huIF-For14 (SEQ ID NO: 12) and ReversePrimer huIF 1248Rev (SEQ ID NO: 13). The RT-PCR profile was as follows:RT step was performed at a temperature of 42° C. for 40 minutes. Thisstep was followed by the PCR step which included one initialdenaturation step at a temperature of 99° C. for 4 minutes; then 43cycles of the following conditions: temperature of 95° C. for 30seconds, then a temperature of 61° C. for 30 seconds, then a temperatureof 72° C. for 1 minute; followed by a final extension at a temperatureof 72° C. for 0.5 minute. This cDNA fragment (1234 bp in length),referred to herein as Porcine IF cDNA₁₄₋₁₂₄₈, (denoted by SEQ ID NO: 4,and its reverse complement SEQ ID NO: 5 and its amino acid sequence SEQID NO: 6) was cloned into the TA cloning vector (pCR 2.1, purchased fromInvitrogen, Carlsbad, Calif.) and transformed into “Top10” E. coli cells(Invitrogen™, Carlsbad, Calif.) to produce the Porcine IF cDNA₁₄₋₁₂₄₈(SEQ ID NO: 5).

The Porcine IF cDNA₁₄₋₁₂₄₈ (SEQ ID NO: 5) was used as the template toproduce the cDNA sequence encoding the porcine intrinsic factor maturepeptide, referred to herein as Porcine IF cDNA₅₄₋₁₂₅₄-Mature Peptide.The nucleotide sequence of the coding strand of Porcine IFcDNA₅₄₋₁₂₅₄-Mature Peptide (1200 bp in length) is denoted by SEQ ID NO:7, its reverse complement is denoted by SEQ ID NO: 8. Translation of theopen reading frame in SEQ ID NO: 7 suggests that porcine intrinsicfactor mature peptide contains 399 amino acids, with an amino acidsequence denoted by SEQ ID NO: 9. The encoded mature peptide has apredicted molecular weight of ˜ 44 kDa.

Using the Porcine IF cDNA₁₄₋₁₂₄₈ (SEQ ID NO: 5) as the template and theForward Primer pIFMP-Forl (SEQ ID NO: 14) and Reverse PrimerpIFMP-RevXhoI (SEQ ID NO: 15), the cDNA encoding the Porcine IFcDNA₅₄₋₁₂₅₄-Mature Peptide was amplified by PCR. The PCR profile was asfollows: one initial denaturation step at a temperature of 95° C. for 5minutes; then 33 cycles of the following conditions: a temperature of95° C. for 30 seconds, then a temperature of 57° C. for 30 seconds, thena temperature of 72° C. for 1 minute; followed by a final extension at atemperature of 72° C. for 5 minutes. This PCR fragment was subclonedinto pGEMEX-1 expression vector (purchased from Promega Corporation,Madison, Wis.). The expressed protein was insoluble and formed inclusionbodies.

To produce a soluble version of this protein, cDNA encoding the PorcineIF cDNA₅₄₋₁₂₅₄-Mature Peptide was amplified by PCR using IF cDNA₁₄₋₁₂₄₈(SEQ ID NO: 5) as the template and the Forward primer pIF-PIC-MP-ForEcoRI (SEQ ID NO: 16) and the Reverse pIF-MP-pMAL-Sal1 Rev primer (SEQID NO: 17) and the following PCR conditions: one initial denaturationstep at a temperature of 95° C. for 5 minutes; then 35 cycles of thefollowing conditions: a temperature of 95° C. for 30 seconds, then atemperature of 56° C. for 30 seconds, then a temperature of 72° C. for 1minute; followed by a final extension at a temperature of 72° C. for 5minutes. The resultant PCR was introduced into the pMAL expressionvector (purchased from Invitrogen, Carlsbad, Calif.) to create theplasmid pMAL-IF. This plasmid (pMAL-IF) produces porcine intrinsicfactor as a fusion protein with Maltose Binding Protein (MBP; molecularweight ˜ 43 kDa). The predicted molecular weight of the pMAL-IF fusionprotein ˜ 87 kDa. The MBP component rendered the porcine intrinsicfactor protein partially soluble.

To further increase the solubility of the protein and to enhance properprotein folding, the cDNA insert encoding the Porcine IFcDNA₅₄₋₁₂₅₄-Mature Peptide was excised from pMAL-IF using therestriction enzymes EcoRI and SalI and inserted into pET32a vector(purchased from Novagen, Madison, Wis.) digested with EcoRI and SalI.This vector produces porcine intrinsic factor as a fusion protein withThioredoxin protein (TrX; molecular weight ˜ 18 kDa). The predictedmolecular weight of the pET32a-IF fusion protein is ˜62 kDa. The TrXcomponent rendered the porcine intrinsic factor protein partiallysoluble.

Example II Expression of Recombinant Porcine Intrinsic Factor in E. coli

Recombinant porcine intrinsic factor was produced in E. coli byexpressing the protein from the pMAL-IF vector as well as the pET32a-IFvector by induction of the T7 promoter using IPTG(isopropyl-beta-D-thiogalactopyranoside). The cells were harvested forthree hours after induction in one case and for four hours afterinduction in another case. The harvested E. coli cells were lysed andthe cell lysate was clarified by centrifugation. The clarified lysatewas loaded onto an anti-intrinsic factor antibody affinity column. Therecombinant intrinsic factor bound to the affinity column. The columnwas washed with phosphate buffered saline (PBS) buffer to remove anyunbound proteins. The intrinsic factor that bound to the column waseluted with glycine buffer. Referring now to FIG. 1, Lane 1 containsmolecular weight markers (marked in kilodaltons). Lanes 2 and 4 containsamples taken at 0 hour post-induction (0 HPI). Lanes 3 and 5 containsamples taken at 4 HPI and 3 HPI. Lane 6 represents the cellpaste (cellsafter concentration and centrifugation). Lane 8 contains the nativeporcine intrinsic factor (purified from hog (Sus scrofa) gut).

Example III Demonstration of the Binding Activity of Porcine IntrinsicFactor

A. Binding to Vitamin B₁₂ in Conjugate Blots

The recombinant porcine intrinsic factor bound to vitamin B₁₂ asdemonstrated using a vitamin B₁₂-Alkaline Phosphatase conjugate blot.The E. coli lysate containing the expressed recombinant porcineintrinsic factor was run on an SDS-PAGE (Polyacrylamide GelElectrophoresis), and the gel was blotted onto nitrocellulose. This blotwas probed with vitamin B₁₂-alkaline phosphatase conjugate and developedusing an appropriate substrate. The recombinant intrinsic factor proteinband developed color, thereby demonstrating that the intrinsic factorbound vitamin B₁₂. Referring now to FIG. 2, Lane 1 contains molecularweight markers (marked in kilodaltons). Lanes 2, 3, 4, and 5 representcells from various clones expressing recombinant porcine intrinsicfactor. Lane 6 contains the native porcine intrinsic factor (purifiedfrom hog (Sus scrofa) gut). The recombinant intrinsic factor proteinband developed color, thereby demonstrating that the intrinsic factorbound vitamin B₁₂.

B. Binding to Anti-Intrinsic Factor Antibody in Western Blots

Binding of the recombinant porcine intrinsic factor to anti-intrinsicfactor antibody was demonstrated by using Western blotting. The E. Colilysate containing the expressed recombinant porcine intrinsic factor wasrun on an SDS-PAGE (Polyacrylamide Gel Electrophoresis), and the gel wasblotted onto nitrocellulose. This blot was probed with anti-intrinsicfactor antibody and developed using an appropriate substrate. Therecombinant intrinsic factor protein band developed color, therebydemonstrating that the recombinant intrinsic factor was recognized bythe antibody. Referring now to FIG. 3, Lane 1 contains molecular weightmarkers (marked in kilodaltons). Lanes 2, 3, 4, and 5 represent cellsfrom various clones expressing recombinant porcine intrinsic factor.Lane 6 contains the native porcine intrinsic factor (purified from hog(Sus scrofa) gut). The recombinant intrinsic factor protein banddeveloped color, thereby demonstrating that the recombinant intrinsicfactor was recognized by the antibody.

C. Feasibility of Using Recombinant Porcine Intrinsic Factor in “AxSYM”and “ARCHITECT” Diagnostic Assays for Vitamin B₁₂

The vitamin B₁₂-binding capacity of the recombinant porcine IntrinsicFactor was measured using in “ARCHITECT” Intrinsic Factor BindingCapacity Assay. The assay is a one-step competitive assay whereintrinsic factor from the test sample competes with intrinsic factorcoated onto microparticles for the vitamin B₁₂-acridinium tracer. Thus,signal in the assay is inversely proportional to the concentration ofintrinsic factor in the test sample. The results are read from a vitaminB₁₂ calibration curve, and the vitamin B₁₂ concentration results areconverted to binding capacity using an equation. The Binding CapacityValue for the recombinant porcine intrinsic factor was determined to be904 ng/ml.

Example IV

The “ARCHITECT” B12 assay is a two-step assay with an automated samplepretreatment, for determining the presence of vitamin B₁₂ in human serumand plasma using Chemiluminescent Microparticle Immunoassay (CMIA)technology with flexible assay protocols. The “ARCHITECT” analyzer andthe method for using the “ARCHITECT” analyzer are described in U.S. Pat.No. 5,795,784, the entirety of which is incorporated herein byreference. The assay for vitamin B₁₂ is described in ARCHITECT™ SystemB12, List No. 6C09, 69-0689/R1, December 1998, Abbott Laboratories,Abbott Park, Ill., the entirety of which is incorporated herein byreference. The sample and Pre-Treatment Reagent 1, Pre-Treatment Reagent2, and Pre-Treatment Reagent 3 are combined. An aliquot of thepre-treated sample is aspirated and transferred into a new reactionvessel. The pre-treated sample, assay diluent, and intrinsic factorcoated paramagnetic microparticles are combined. Vitamin B₁₂ present inthe sample binds to the intrinsic factor coated microparticles. Afterwashing, vitamin B₁₂-acridinium-labeled conjugate is added in the secondstep. The vitamin B₁₂-acridinium-labeled conjugate is capable ofundergoing a chemiluminescent reaction. Pre-Trigger and Triggersolutions are then added to the reaction mixture; the resultingchemiluminescent reaction is measured as relative light units. Aninverse relationship exists between the amount of vitamin B₁₂ in thesample and the relative light units detected by the “ARCHITECT” ioptical system. Further details on the system and assay technology canbe found in “ARCHITECT” i System Operations Manual, the entirety ofwhich is incorporated herein by reference. The reagents for the assayare described below (the amounts per bottle are for 100 tests):

Porcine intrinsic factor coated Microparticles in borate buffer withprotein (bovine) stabilizers. Preservative: antimicrobial agents. (1bottle, 6.6 mL/bottle)B12 acridinium-labeled Conjugate in MES buffer. Minimum concentration:0.7 ng/mL. Preservative: antimicrobial agent. (1 bottle, 5.9 mL/bottle)B12 Assay Diluent containing borate buffer with EDTA. Preservative:antimicrobial agents. (1 bottle, 10 mL/bottle)B12 Pre-Treatment Reagent 1 containing 1.0 N sodium hydroxide with0.005% potassium cyanide. (1 bottle, 27 mL/bottle)B12 Pre-Treatment Reagent 2 containing alpha monothioglycerol and EDTA.(1 bottle, 5.5 mL/bottle)B12 Pre-Treatment Reagent 3 containing cobinamide dicyanide in boratebuffer with protein (avian) stabilizers. Preservative: Sodium Azide. (1bottle, 5.5 mL/bottle)“ARCHITECT” i Multi-Assay Manual Diluent containing phosphate bufferedsaline solution. Preservative: antimicrobial agent. (1 bottle, 100mL/bottle)“ARCHITECT” i Pre-Trigger Solution containing 1.32% (w/v) hydrogenperoxide.“ARCHITECT” i Trigger Solution containing 0.35 N sodium hydroxide.“ARCHITECT” i Wash Buffer containing phosphate buffered saline solution.Preservative: antimicrobial agent.

Example V

The “AxSYM” B12 assay is based on the Microparticle Enzyme Immunoassay(MEIA) technology. The “AxSYM” analyzer and the method for using the“AxSYM” analyzer are described in U.S. Pat. No. 5,358,691, the entiretyof which is incorporated herein by reference. The assay for vitamin B₁₂is discussed in Abbott AxSYM® System B12, List No. 3C79, 69-0912/R2,February 1999, Abbott Laboratories, Abbott Park, Ill., the entirety ofwhich is incorporated herein by reference.

The “AxSYM” B12 reagents and sample are pipetted in the followingsequence:

The sample and all “AxSYM” B12 reagents required for one test arepipetted by the Sampling Probe into various wells of a Reaction Vessel.Extractant 1 and Extractant 2 are combined in one Reaction Vessel well.Sample, Denaturant, and a portion of the Extractant mixture are combinedin another Reaction vessel well. The Reaction Vessel is immediatelytransferred into the Processing Center. Further pipetting is carried outin the Processing center with the Processing Probe. Intrinsic factorcoated microparticles are added to the reaction mixture. Vitamin B₁₂present in the sample binds to the intrinsic factor coatedmicroparticles forming a complex containing vitamin B₁₂ and intrinsicfactor coated microparticles. An aliquot of the reaction mixture istransferred to the matrix cell. The microparticles bind irreversibly tothe glass fiber matrix. The matrix cell is washed to remove materialsnot bound to the microparticles. The vitamin B₁₂:Alkaline PhosphataseConjugate is dispensed onto the matrix cell, thereby forming a complexcontaining vitamin B₁₂, intrinsic factor coated microparticles, andconjugate. The vitamin B₁₂:Alkaline Phosphatase Conjugate is capable offorming a fluorescent product. The matrix cell is washed to removeunbound conjugate. The substrate, 4-Methylumbelliferyl Phosphate, isadded to the matrix cell and the fluorescent product is measured by theMEIA optical assembly. The substrate, 4-Methylumbelliferyl Phosphate, isa fluorogenic material. Further details on the system and assaytechnology can be found in “AxSYM” System Operations Manual, theentirety of which is incorporated herein by reference. The reagents forthe assay are described below (the amounts per bottle, for the items inthe REAGENT PACK, are for 100 tests):

Reagent Pack B12 Denaturant

B12 Denaturant: 0.8 N Sodium Hydroxide with 0.005% Potassium Cyanidesupplied in a separate bottle from the Dual Pack (1 bottle, 13.0 mL/perbottle)

Reagent Pack A

Extractant 1. Cobinamide Dicyanide in borate buffer with protein (avian)stabilizer. Preservative: Sodium Azide. (1 bottle, 8.7 mL/bottle)Extractant 2. Alpha Monothioglycerol in EDTA. (1 bottle, 3.8 mL/bottle)Porcine Intrinsic Factor Coated Microparticles in borate buffer withprotein (bovine) stabilizer. Preservative: Sodium Azide. (1 bottle, 14.1mL/bottle)

Reagent Pack B

B12:Alkaline Phosphatase (bovine) Conjugate in TRIS buffer with protein(bovine) stabilizer. Minimum concentration: 0.1 μg/mL. Preservative:Sodium Azide. (1 bottle, 12.5 mL/bottle)B12 Denaturant. 0.8 N Sodium Hydroxide with 0.005% Potassium Cyanide. (1bottle, 13.0 mL/bottle)Porcine Intrinsic Factor Coated Microparticles in borate buffer withprotein (bovine) stabilizer. Preservative: Sodium Azide. (1 bottle, 14.1mL/bottle)

Other Reagents (not in Reagent Pack)

Solution 1 (MUP) contains 4-Methylumbelliferyl Phosphate, 1.2 mM, in AMPbuffer. Preservative: Sodium Azide. (4 bottles, 230 mL/bottle)Solution 3 (Matrix Cell Wash) contains 0.3 M sodium chloride in TRISbuffer. Preservatives: Sodium Azide and Antimicrobial Agents (4 bottles,100 mL/bottle)Solution 4 (Line diluent) contains 0.1 M phosphate buffer.Preservatives: Sodium Azide and Antimicrobial Agent (1 bottle, 10L/bottle)AxSYM Probe Cleaning Solution contains 2% Tetraethylammonium Hydroxide(TEAH) (2 bottles, 220 mL/bottle)

Porcine intrinsic factor coated microparticles are typically made ofmaterial such as polystyrene and they range from about 0.5 micrometer toabout 15 micrometer in diameter. The microparticles have functionalgroups on the surface thereof, such as, for example, carboxyl groups oramino groups, which are used for coupling to proteins or othermolecules. This coupling can be passive or active. In active coupling,an activating reagent, such as, for example, EDAC, is used.

For porcine intrinsic factor coated microparticles for use in the“ARCHITECT” B12 assay, the porcine intrinsic factor is covalentlycoupled to Carboxylated Microparticles by using EDAC activation method.EDAC (1-ethyl-3-(-dimethylaminopropyl)-carbodiimide hydrochloride) isused to activate carboxyl groups on the microparticle, which groups canundergo coupling with amino groups on the protein (i.e., the porcineintrinsic factor).

For porcine intrinsic factor coated microparticles for us in the “AxSYM”B12 assay, the anti-intrinsic factor antibody is first coupled to themicroparticles using EDAC. Then the porcine intrinsic factor is added tothese microparticles. The porcine intrinsic factor binds to theanti-intrinsic factor antibody coated on the microparticles, whereby themicroparticles are now coated with porcine intrinsic factor.

The loading of porcine intrinsic factor on the microparticles isdetermined by the designer of the assay, and the proper loading canreadily be determined by one of ordinary skill in the art.

The nucleotide and amino acid sequences referred to in the specificationare listed below:

1. An isolated nucleic acid sequence or fragment thereof comprising orcomplementary to a nucleotide sequence encoding porcine intrinsicfactor, wherein the amino acid sequence of said porcine intrinsic factorhas at least 85% identity to an amino acid sequence selected from thegroup consisting of SEQ ID NO: 3, SEQ ID NO: 6, and SEQ ID NO:
 9. 2. Thenucleotide sequence of claim 1 wherein said sequence is isolated fromSus genus.
 3. The nucleotide sequence of claim 2 wherein said species ofsaid Sus genus is Sus scrofa.
 4. An isolated nucleic acid sequence orfragment thereof comprising or complementary to a nucleotide sequencehaving at least 85% identity to a nucleotide sequence selected from thegroup consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO:
 7. 5. Thenucleotide sequence of claim 4 wherein said sequence is isolated fromSus genus.
 6. The nucleotide sequence of claim 5 wherein said species ofsaid Sus genus is Sus scrofa.
 7. A method of producing porcine intrinsicfactor comprising the steps of: (a) isolating a nucleic acid sequencecomprising or complementary to a nucleotide sequence: i) encodingporcine intrinsic factor comprising an amino acid sequence having atleast 85% identity to an amino acid sequence selected from the groupconsisting of SEQ ID NO: 3, SEQ ID NO: 6, and SEQ ID NO: 9, or ii)having at least 85% identity to a nucleotide sequence selected from thegroup consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO: 7; (b)constructing a vector comprising: i) said isolated nucleotide sequenceoperably linked to ii) a regulatory sequence; (c) introducing saidvector into a host cell for a time and under conditions sufficient forexpression of said porcine intrinsic factor.
 8. A vector comprising: (a)an isolated nucleic acid sequence comprising or complementary to anucleotide sequence: i) encoding a polypeptide comprising an amino acidsequence having at least 85% identity to an amino acid sequence selectedfrom the group consisting of SEQ ID NO: 3, SEQ ID NO: 6, and SEQ ID NO:9, or ii) having at least 85% identity to a nucleotide sequence selectedfrom the group consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO:7, operably linked to (b) a regulatory sequence.
 9. An isolated nucleicacid sequence or fragment thereof which hybridizes, under moderate orhigh stringency conditions, to a nucleic acid sequence selected from thegroup consisting of SEQ ID NO: 1, SEQ ID NO: 4, and SEQ ID NO:
 7. 10. Anisolated nucleic acid or fragment thereof, which hybridizes, undermoderate or high stringency conditions, to an isolated nucleic acidsequence encoding porcine intrinsic factor, wherein the amino acidsequence of said polypeptide has at least 85% identity to an amino acidsequence selected from the group consisting of SEQ ID NO: 3, SEQ ID NO:6, and SEQ ID NO: 9.